This invention relates to connection between two rotating components, and, more particularly, to an electromagnetically formed joint and method of forming the same to join a machine element, such as a gear, pulley, cam, sprocket and the like to a shaft for transmitting power between the machine element and the shaft.
One of the most common mechanical elements in the design of machines and drive trains is the use of gears to transmit rotational power, and one typical type of gearing is bevel gears which are used universally to connect non-parallel shafts that may be intersecting or non-intersecting. The present invention, for convenience, will be described specifically with reference to bevel gears, however, it will readily be seen that the invention can be used to affix any type of gear to a gear shaft including, but not limited to, spur gears, worm gears, helical gears and the like. In similar manner, the invention can be used to secure cams, sprockets, pulleys to a shaft or even to unite other rotating components such as shafts
Turning, however to t hie use of bevel gears to provide one illustration of the use of the invention, in general, the shafts of bevel gears meet and thus connect at an angle of 90 degrees, however, other angles are certainly used with the bevel gear connections.
In the construction of bevel gearing, generally the gears themselves are contained within a gearbox such that the ends of the operative shafts extend through the gearbox for connection to the input and output mechanisms through couplings. There are times where it is advantageous for the bevel gearbox to be constructed so as to have a two piece gear/shaft, that is, the gear is internally connected within the gearbox to a shaft that, in turn, extends external to the gearbox for further connection to a component.
There are various reasons to select a two piece gear/shaft and such rationale may depend upon the cost of the materials, machining and assembly time. In any event, the construction of a bevel gearbox containing a two piece gear/shaft is, at times, very desirable and an efficient, positive joint between the two components is therefore needed. One difficulty, however, is that the juncture of the bevel gear hub and the shaft is an important, crucial connection and must be strong yet be such that the joint is contained within the gearbox. Thus, the formation of such joint is critical and it would be advantageous to bring about an improvement in the strength of the joint as well as the ability to easily and reliably create that connection.
With current practice, the connection between the hub of a bevel gear, as well as the connection between most gears, is accomplished in a variety of ways, including the use of bolt flanges, splines, welding and the like and each technique has certain advantages and disadvantages.
The use of electromagnetic forming of metals is currently known and used in a variety of applications where the deformation of a conductive material is desired. In particular, the process, often called magneforming, is a technique that utilizes an intense transient magnetic field to shape metal and comprises the use of a formation of the magnetic field between a coil and the metal workpiece to be formed. The intense magnetic field is generated by means of a high pulse of electric current that is passed through the coil positioned near the metallic material to be deformed. As the intense magnetic field is generated, there is a powerful mutual repulsion created between the coil and the workpiece. The coil itself is made of substantially strong materials such that the repulsion stresses the workpiece beyond its yield strength and causes deformation in the desired amount.
The use of magneforming is shown and described in U.S. Pat. No. 2,976,907 in its basics and is further described for certain applications in U.S. Pat. No. 5,692,853 of Litz et al where the deformation is used to interfit threads of a joint together. Other examples of magneforming are found in U.S. Pat. No. 3,837,755; U.S. Pat. No. 4,513,488 and U.S. Pat. No. 4,561,799.
Accordingly, since the technology of magneforming exists, it would be advantageous to make use of that technology to solve a problem in the joining of the bevel gear, or, for that matter, any type of gear, to a shaft that would result in an efficient, strong and easily formed joint between those components.
Now, in accordance with the present invention, there is provided a joint adapted to be used between a hub of a bevel gear and a shaft that then extends from that gear and which joint can be easily formed. In the formation of the joint, the hub of the bevel gear is configured in a particular shape and an external configuration of the shaft affixed to the bevel gear is also configured to be in the same shape as the gear hub. In the preferred embodiment, the shape is that of a polygon and the invention will further be described with respect to that configuration, however, it will be seen that other configurations are applicable providing the gear hub and the shaft eternal configuration be similar so as to be aligned together abutting each other to form a contiguous surface to carry out the present invention. Thus, the two eternal surfaces of the components to be joined together are of the same polygon configuration and are aligned so as to mate with each other with the polygon shapes in alignment.
A metallic cylindrical torque ring surrounds the ends of the bevel gear hub and the end of the shaft affixed thereto and is deformed to be compressed about the polygonal surfaces of each of those components to join the bevel gear hub to the shaft. In carrying out the deformation, the cylindrical ring surrounds at least the two mating polygonal surfaces and the cylindrical ring is slightly longer than the combined length of the polygonal surfaces.
To effect the joint, therefore, a coil is located exteriorly of the metallic cylindrical torque ring and the intense charge of electric current applied to the coil. As the mutual repulsion is thus created between the exteriorly located coil and the metallic cylindrical torque ring, the coil is sufficiently strong to not deform, but that repulsion causes the cylindrical torque ring to deform inwardly to be tightly wrapped around the external polygonal surfaces of the hub of the bevel gear and the raised surface of the shaft, thereby forming a strong joint between the shaft and the bevel gear. The excess length of the cylindrical torque ring that extends beyond the combined lengths of the polygonal surfaces is also deformed inwardly and envelopes the free ends of those surfaces, thereby retaining the bevel gear to the shaft axially.
The deformation or compression of the cylindrical torque ring on to the joined bevel gear hub and shaft is relatively easy to carry out and yet the overall joint is a strong coupling and can be located within the gearbox of the bevel gears. Additionally, the particular method of carrying out the joint is a low cost procedure and is readily adaptable to automated processes. In such joints, therefore, the resultant joint is strong and certainly capable of joining the bevel gear, or other type of gear, to a shaft and that joint is able to fit within and thus be fully located within the gearbox of the particular gearing.
Typical of such joints between a bevel gear hub and a shaft, the cylindrical torque ring carries pure torque between the shaft and the bevel gear as the thrust is transmitted directly into the raised portion of the shaft and not through the torque ring. As such, therefore, the actual coupling of the gear on to the shaft need only be a light press fit for purposes of accurate diametral location since the torque is actually transmitted between the gear hub and the raised surface of the shaft acting through the metallic torque ring. Therefore, an interference fit is not required to press the gear on to the shaft since the actual affixation of the gear to the shaft is not critical in transmitting torque between the two components. In addition, the axial thrust is carried by means of the gear hub abutting against a shoulder formed by the raised surface of the gear shaft which transmits the thrust load through the support bearing into the housing. Thus, doe to the construction of the joint of the present invention, the torque ring handles no radial loads and no axial loads but transfers only pure torque between the rotating components.
Thus, the joint between the two components and the method of making that joint can be carried out easily to provide a strong joint between the shaft and the hub of the bevel gear. The joint can be readily located within the gearbox of the bevel gears and yet the strength of the joint is such that it can easily transmit the torque between the bevel gear and the shaft extending external of the bevel gearbox. In similar fashion, the method of forming and the joint itself are equally applicable to other gears and machine elements and the joining of such other gears or machine elements to shafts or even the joining of shafts together.
Other features and advantages will become apparent to those skilled in the art from a review of the ensuing description which proceeds with reference to the following illustrative drawings: